The Stovebolt Site Forums The Shop Area Engine Shop 347 Pontiac carb

I would like to change out the the carb in my 57 GMC one ton it has the 347 pontiac and the carb in it is beyond rebuild some one in the past cracked the casing and put what looks like JB welded over the crack, the choke arm is missing it is a pos. I would like to put a new four barrel on it but finding a four barrel intake for a 347 that will work with modern carbs has so far been hard to do. Will a intake off a 326 or 389 work and what years will bolt up? or other options?
Thanks

Boy that is a good question.
I might suggest you check out the H.A.M.B. forum. It's a bunch of hotrodders for all makes and models.

You'll have to join up first, but it's worth it, you'll probably like it.
http://www.jalopyjournal.com/forum/

I believe you are looking for manifolds from 1957-1960 only. Check ebay, Wallace Racing, Butler Performance, Pontiac Safari.

There are both factory and after market manifolds available to work. Is your 2bbl a rochester or a stromberg ww? The GMC 347 had a large 2bbl manifold with an adapter for a small stromberg ww carb. A larger Rochester might due what you want.

My 59 GMC has a 59 Pontiac 389 that has been stroked to 447 with a 57 Pontiac tripower manifold. The trips are a great combination.

The easiest and cheapest thing to do would be to replace the 2bbl with the another 2bbl.

1955-1960 manifolds should bolt up.

The manifold ports MAY be larger than the head ports for the 347 truck engine.

Modern carburetors will not fit the pre-1961 manifolds (and the post 1960 manifolds will not fit the pre-1961 heads). This is a good thing. The modern AFB clones will need major surgury to perform correctly on the 347 (primary clusters, secondary clusters, auxiliary air valve, primary jets, secondary jets, metering rods, and vacuum springs will ALL need to be changed)!

If you want a four barrel, find a 1957~1960 Pontiac manifold with carburetor, and rebuild it.

Jon.

Jon that is not the answer I was looking for but thanks for the information it seams like I would be better finding a 2bbl to replace the one I have. Thanks for the info guys

In 1957, Pontiac used both the Rochester 4-GC and the Carter AFB. For reasons I won't discuss in this thread, the Carter is MUCH HIGHER priced. However, the Rochester is an EXCELLENT four barrel. If you want a four barrel, find a used one and manifold, and rebuild the 4-GC.

A Rochester 2-GC from a Pontiac 370 or 389 might be another option, but the four barrel with the small primaries would be easier to tune to the 347 than would the two barrel.

The Stromberg two barrel type WW carburetors are excellent carburetors, but very scarce and difficult to locate for the GMC engine.

The four barrel should give a modest increase in performance (power, driveability, AND economy); but not as much as if you also changed other components of the engine (cam, compression, exhaust, etc.).

Jon.

Performance is not my main goal proper running condition is. What 2bbl wold bolt on and be easy to find if there is such a thing

Don't know. The Rochester two barrel that is internally sufficiently large to support the 347 used a different flange mounting than the Stromberg.

Jon.

The stromberg ww used a cast iron adapter flange on the gmc engines. I suspect a large base rochester will fit the manifold without the adapter.